Abrasive blasting apparatus



FLG. 2

Aug. 7, 1962 Filed Sept. 1, 1961 G. W. M KULLA, JR

ABRASIVE BLASTING APPARATUS 2 Sheets-Sheet l INVENTOR ATTORNEZS GEORGE WNi KULLA ,JR.

1962 G. w. M KULLA, JR 3,047,986

ABRASIVE BLASTING APPARATUS Filed Sept. 1, 1961 2 Sheets-Sheet 2 n 5 AIRABRASNE FLGS. 1, 2O 1B 22 INVENTOR ATTORNEYS GEZSiiE W. MCKULLAJR.

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The present invention relates to abrasive blasting apparatus, and moreparticularly to means for instantly and effectively relieving orclearing the blast nozzles of such apparatus when they become plugged orclogged during use.

More specifically, the invention is directed to the provision of a noveldevice for clearing plugged or clogged sand blasting nozzles as used inthe brick-making art for applying a decorative finish to one or morefaces of bricks while in the uncured condition.

The sand blasting nozzles of brick facing machines often become cloggedwith agglomerated masses of sand and/ or impurities such as brickcuttings which find their way into the sand supply. Another practice inthe brickmaking art which contributes to frequent clogging of sandblasting nozzles is that of intermixing colored pigments with the sandfor the purpose of producing bricks having sand finishes of variouscolor tones. Because the granules of sand tend to adhere and stick tothe particles of pigment and then to each other, even when beingsubjected to the aspirating action of a high pressure air jet, thenozzles of sand blasting guns using sand-pigment mixtures become jammedor plugged at rather frequent intervals.

In the past, whenever nozzle clogging has occurred, it'

has been necessary to shut down the entire brick-making production lineWhile identifying the particular nozzle which is obstructed and theneither manually disassembling and cleaning the nozzle, or manuallycovering the discharge orifice of the nozzle with a suitable plate or aworkmans glove while another workman directs high pressure air into thegun to back-blow the clogging mass through the sand feed line. Theseknown procedures involve both lost production time and additional labor,and are therefore quite costly when computed over an extended period oftime.

The principal object of the present invention is to provide new andimproved means for clearing obstructions from the nozzles of abrasiveblasting guns which are operable by a single workman without thenecessity of stopping production or dismantling the equipment, and whichthereby overcome the deficiencies and disadvantages of the practices ofthe prior art.

Another primary object of this invention is to provide a structurallysimple, highly eifective device for cleaning out plugged or clogged sandblast nozzles which is adapted for direct and permanent attachment tothe nozzle itself, but is operable from a position remote from thenozzle.

A further object is to provide a novel device for clearing plugged sandblast nozzles which is of inexpensive, durable construction embodying aminimum of parts, and is effective and reliable in operation.

Still another object is to provide a device of the character describedwhich comprises a member supported on the nozzle of an abrasive blastinggun which is movable into and out of the path of the air-borne abrasivestream issuing from the nozzle and is operable to close the nozzledischarge orifice so as to effect back-blowing of the high pressure airand thereby dislodge from the interior of the gun whatever obstructionmay exist therein.

These and other objects and advantages of the invention will become moreapparent from the following de- Patented Aug. 7, 1962 tailed descriptionof the embodiments illustrated in the accompanying drawings, wherein:

FIG. 1 is a front elevation view of a typical abrasive blastinginstallation adapted for the sand facing of bricks or the like whichincorporates one embodiment of the present invention, certain portionsof the sanding cabinet being broken away to more clearly disclose theabrasive guns and the associated nozzle clearing mechanism;

FIG. 2 is a side elevation of the installation shown in FIG. 1;

FIG. 3 is an enlarged perspective View of one of the abrasive guns andassociated nozzle clearing means shown in FIG. 1;

FIG. 4 is a vertical cross-sectional view of the assembly of FIG. 3,showing the nozzle clearing means in its normally retracted orinoperative position;

FIG. 5 is a cross-sectional view similar to that of FIG. 4, but showingthe nozzle clearing mechanism in its operative position; and

FIG. 6 is a fragmentary diagrammatic view of a modified form of nozzleclearing mechanism adapted for electrical actuation.

Referring first to FTGS. 1 and 2 of the drawings, there is showngenerally at A an apparatus for providing a decorative sand finish onone or more faces of bricks or similar articles which comprises aframework B for sup porting an elevated cabinet or casing C wherein arehoused a plurality of abrasive or sand blasting guns G and associatednozzle clearing mechanisms N. As illus trated by the representation of aworkman M depicted in broken outline in FIG. 1, the apparatus A isrelatively large in size and is interposed between two elevatedconveyors 10 and 10', the conveyor 10 serving to deliver uncured bricksfrom the usual extruder and automatic cutting machine (not shown) to thesanding cabinet C, while conveyor 10', which is driven at a faster speedthan conveyor 16), carries the sanded brick column away from the cabinetpast an inspection station to a point at which the bricks are loadedonto pallets prior to delivery to the curing or burning kilns. Ifdesired, the conveyor 16 may be extended so as to pass through thecabinet C and deliver the bricks directly to conveyor 10'.

The sanding cabinet C is generally rectangular in form and comprisesside walls 11, front and rear walls 12 and 13, respectively, and a topwall 14. The bottom of the cabinet is formed by the sloping walls 15 ofa pair of truncated sand hoppers H which are separated as shown in FIG.1 by a central passageway P and deliver sand by gravity into a pair ofsupply hoppers S which are open at the sides to receive the suction orintake ends of a plurality of flexible abrasive-resistant conduits orhoses 16 through which sand is fed to the guns G. The cabinet C is alsoprovided with a pair of normally closed access doors D which permitaccess to the guns G and their adjustable mounting means 17 within thecabinet.

In order to produce a decorative sanded finish on bricks, blasts of sandare discharged from the guns G againstthe top and/0r side faces of thesoft uncured bricks as they enter the cabinet C through an opening inthe front wall 12 and are pushed through the cabinet along a deliveryplate 18 which closes the upper end of passageway P and bridges the gapbetween conveyors 10 and 10'. The sanding is achieved in the usualmanner by aspirating the sand from the supply hoppers S through hoses 16into the guns G by the injector action of a fluid under pressure. In theapparatus illustrated, compressed air is supplied from a main header 19through a plurality of individually valve-controlled conduits 20 ofreduced cross-section to the guns G. As shown in FIGS. 4 and 5, each gunG includes a venturi type air jet nozzle 21 which isremovably mounted inthe gun body in axial alignment with a detachable blast nozzle 22 havinga disspar/pee charge orifice 23, and to which one of the air deliveryconduits 2% is connected. The air issuing from jet nozzle 21 and flowingoutwardly through blast nozzle 22 normally causes sand to be drawnthrough hose 16, which is connected to an angularly offset portion 24 ofthe gun body, into the area 25 where the sand and air are mixed to forma high velocity air-borne stream of abrasive ma terial. To facilitatethe continuous gravity feed of sand from hoppers S into hoses to, thesuction ends 26 of the latter may be beveled, as indicated in FIG. 1.

-For the purpose of further enhancing the decorative finish of thebricks, the supply of sand in the hoppers H and S is frequently mixedwith various colored pigments to produce a variety of color-toned sandedbricks. As a result of this practice, the gun nozzles 22 become cloggedat unduly frequent intervals at their inlet ends because the pigmentparticles tend to cause the sand granules to stick together and to buildup obstructions, particularly in the restricted passageways 27 aroundjet nozzles 21 leading to the mixing areas or chambers 25. Clogging alsooccurs due to the presence in the sand of brick cuttings and otherforeign matter, or when the sand is wet. Heretofore, when such cloggingoccurred it was necessary for a workman to climb up on the cabinet C,open the double access doors D, identify the clogged gun nozzle, andthen, after stopping the entire assembly line and shutting oif the airto all guns, either unscrew the nozzle and clean out the obstruction, ormanually place a plate or heavy pad tightly over the discharge orifice23 while having another workman open the air line to the clogged gunafter removing the suction end 26 of the associated feed hose 16 fromthe supply hopper S and directing it toward a refuse collectingreceptacle 28, as indicated in FIG. 1. By the latter procedure, the airflows back from the closed end of the nozzle, through the mixing chamber25 and passageway 27, and out the feed hose 16, carrying with itwhatever sand, pigment or foreign matter may have caused theobstruction.

As previously stated, the nozzle clearing mechanism N forming thesubject matter of the present invention overcomes the disadvantages ofthe time-consuming and costly procedures of the prior art in a simple,efiicient and inexpensive manner, and may be operated from floor levelexteriorly of the cabinet C, either by hand-pull means 29 as shown inFIGS. 1 and 2, or by electrical solenoid means 3!) and push buttons 31as depicted in FIG. 6.

The details of the mechanism N are best seen in FIGS. 3, 4 and 5. Asthere shown, each gun G is provided with a supporting bracket or frame32 which is rigidly mounted on and secured to the nozzle 22, onepractical form of said bracket being generally U-shaped as shown,fabricated of a durable strap material, and having a neck 33 which isclamped around nozzle 22 and a pair of parallel arms 34 which are joinedtogether in spaced relationship by screws or bolts 65 surrounded byspacer sleeves 36. The arms 34 project substantially at right anglesfrom the axis of the gun nozzle 22, and support a selectively movableL-shaped lever '37 for pivotal movement about a pivot pin 38 whichpasses through lever 37 at a point adjacent the end of the shorter armthereof. Lever 37 carries at the end of its longer arm a plate 39 towhich is fixed a plug 40 of abrasive-resistant rubber or other resilientmaterial adapted to close and seal the orifice 23 of nozzle 22 when thelever 37 is moved into the position shown in FIG. 5. In order tonormally maintain the nozzle closing assembly comprising lever 37, plate39 and plug 40 out of the path of the air-borne stream of sand whichissues from nozzle 22 and thereby avoid abrasive damage to said assemblya pair of tension springs 41 are suitably connected between the outerends 42 of bracket arms 34 and the outer free end of the lever 37beneath plate 39, the direction of pull of springs 41 relative to pivotpin as being such as to yieldably urge lever 37 into the position shownin FIG. 4.

Means are also provided for selectively moving each lever 37 and theassociated plate 39 and plug as into the nozzle closing positionillustrated in FIG. 5 whenever it is desired to clear the gun of anobstruction, which means are operable from a location remote from thegun. in the installation depicted in FIGS. l5, the operating meanscomprise a cable 43 of stainless steel or other suitable material oneend of which passes between the spacer sleeves 36, the rounded surfacesof which offer a minimum of frictional resistance to movement of thecable, and is attached :to the longer arm of lever 37 at a point d -tinwardly of plate 39. The rest of cable 43 is trained over a rounded rod45 forming part of the gun mounting means 17, or over a pulley mountedon said rod, and then passes through an aperture in one of side walls11, over another anti-friction means or pulley 46 disposed ex- :teriorlyof the cabinet C, and downwardly to a point adjacent the hopper S andreachable from the floor level, at which point the cable terminates in atoggle or other suithand-pull member 29. As will be seen from FIGS. 1and 2, the portion of each cable 43 outside cabinet C parallels and isclosely adjacent the sand feed hose 16 which leads to the same gun G asthat whose nozzle clearing mechanism N is operable by said cable, andeach hand-pull member 29 is so located that a workman may grasp saidmember and pull the cable with one hand while simultaneously withdrawingthe suction end 26 of the associated hose 16 from the hopper S anddirecting it toward the refuse receptacle 28 with his other hand.

The modified form of the invention illustrated diagrammatically in FIG.6 ditfers from that shown in FIGS. 15 only in that the outer end of eachcable 4-3 is connected to the plunger of a solenoid 30 which is mountedon one of side walls 11 exteriorly of cabinet C, and a push button 31 isprovided for energizing the solenoid from any suitable source ofelectrical power whenever it is desired to actuate the nozzle closingmeans to which the cable is connected. It will also be understood thatthe push buttons 31 are located at substantially the same positions asthe toggles 29 of FIGS. 1 and 2 so that one work man can simultaneouslyclose the blast nozzle and handle the suction end of the sand supplyhose of any selected gun.

In operation, the supply hoppers S are fed from main hoppers H which areperiodically filled with sand or other abrasive material, mixed withcolored pigments when desired, through filling chutes 47 supported onthe rear wall 13 of the cabinet C. The sand feeds by gravity from chutes4'7 into hoppers H through openings 48 in wall 13 and then into thelower hoppers S into which the beveled suction ends 25 of the abrasivesupply conduits or hoses 16 are removably inserted. A downwardlyinclined plate 49 is mounted above each opening 48 and across the upperportion of each hopper H to prevent the spent sand and pigment particlesfrom re-collecting in said hopper. Openings 50 are provided in the frontwall 12 of the cabinet adjacent the lower ends of plates 49 throughwhich the spent abrasive material may be periodically discharged.

The hoses to normally deliver sand to the guns G, four of which may bedisposed in two pairs directed angularly downward and inward fromopposite sides of the cabinet C toward the end faces and portions of thetop faces of the bricks on the delivery plate 18, and while twoadditional pairs may be mounted above the bricks for downward dischargeonto the top surfaces of the bricks. Compressed air is also normallydelivered to each gun G through one of the valve-controlled air deliveryconduits 20 connected to the main air supply header 19 which extendslaterally across the rear wall 13 of the cabinet C. As the uncuredbricks pass through the cabinet on the plate 18, a sand facing may beapplied to one or more of the exposed faces thereof by simply openingthe individual air valves V (FIG. 2) of whichever of guns G it isdesired to use.

As long as all of the guns G then in use function normally by directingair-borne streams of abrasive material against the exposed faces of thebricks, the nozzle clearing mechanisms N are retained in theirretracted, in operative positions by the springs 41. However, wheneverthe operator observes that one of the guns ceases to deliver a properabrasive blast due to clogging of the nozzle, he can quickly andeffectively clear the obstructed nozzle, in a matter of a few seconds,by simply withdrawing the suction end 26 of the associated flexible sandconduit 16 from the hopper S and directing it toward the wastereceptacle 28, while pulling down on the proper hand-pull member 29' andthe cable 43 connected thereto so as to close the discharge orifice 23of the clogged nozzle, whereupon the compressed air delivered to thatgun is deflected back through the nozzle and forces the obstructing sandand other matter out of the gun through the conduit 16 and into thereceptacle 28, as indicated in FIG. 1. When the nozzle has been cleared,the handpull member 2% is released, thereby permitting the springs 41 toreturn the nozzle closing lever 37, plate 39* and plug 40' to theirnormal retracted position, and the suction end 26 of conduit 16 isreinserted into the sand supply hopper S, whereupon sand is again fed tothe associated gun.

The solenoid actuated arrangement shown in FIG. 6 operates in the samemanner .as above described except that the cables 43 are pulled by thesolenoids 30 whenever the push button switches 31 are closed.

It will be apparent from the foregoing disclosure that the nozzleclearing mechanism of the present invention fully achieves the objectsand advantages set forth in the preamble of this specification. Whilethe specific installation described and illustrated herein is related tothe brickmaking art and is intended for the purpose of providing sandedfaces on bricks, it is to be expressly understood that the invention isapplicable to other types of abrasive blasting apparatus, includingthose using abrasive materials other than sand.

It will also be obvious that the invention is not limited to theparticular devices shown in the drawings, but is capable of a variety ofmechanical embodiments, and that various changes, which will now suggestthemselves to those skilled in the art, may be made in the form, detailsof construction and arrangement of the parts without departing from theinventive concept. Reference should therefore be had to the appendedclaims for a definition of the scope of the invention.

What is claimed is:

1. In an abrasive blasting apparatus of the type embodying a pluralityof abrasive guns mounted in a normally closed cabinet for directingair-borne streams of abrasive material against exposed surfaces ofarticles within the cabinet which are to be abraded, each of said gunsincluding a passageway through which abrasive particles are aspiratedfrom a supply line by a jet or" air under pressure, a chamber in whichsaid particles are mixed with the air to form an air-borne abrasivestream, .and a blast nozzle having an orifice from which the abrasivestream is discharged, and wherein the abrasive material tends to clog upand form obstructions in said passageway during operation of theapparatus; the combination with said apparatus of means for clearingsaid nozzles when clogged comprising a member movably mounted on each ofsaid abrasive guns for closing the discharge orifice of the nozzlethereof, means for normally retaining each of said members out of thepath .of the abrasive stream issuing from said nozzle, and

team operable from a position remote from said guns for selectivelymoving each of said members into a position wherein it closes thedischarge orifice of the associated nozzle and thereby causes the air toflow back into .the abrasive supply line through said passageway andclear whatever obstruction may exist therein.

2. in an abrasive blasting apparatus of the type embodying a pluralityof abrasive guns mounted in a normally closed cabinet for directingair-borne streams of abrasive material against exposed surfaces ofarticles within the cabinet which are to be abraded, each of said gunsincluding a passageway through which abrasive particles are aspiratedfrom a supply line by a jet of air under pressure, a chamber in whichsaid particles are mixed with the air to form an air-borne abrasivestream, and a blast nozzle having an orifice from which the abrasivestream is discharged, and wherein the abrasive material tends to clog upand form obstructions in said passageway during operation of theapparatus; the combination with said apparatus of means for clearingsaid nozzles when clogged comprising a member supported on the nozzle ofeach of said abrasive guns for move ment toward and away from thedischarge orifice of said nozzle, yieldable means for normally retainingeach of said members out of the path of the abrasive stream issuing fromsaid nozzle, and means operable from a position outside the cabinet ofsaid apparatus for moving each of said members individually into aposition wherein it closes the discharge orifice of the associatednozzle and thereby causes the air to flow back into the abrasive supplyline through said passageway and clear whatever obstruction may existtherein.

3. In an abrasive blasting apparatus of the type embodying a pluralityof abrasive guns mounted in a normally closed cabinet for directingair-borne streams of abrasive material against exposed surfaces ofarticles within the cabinet which are to be abraded, each of said gunsincluding a passageway through which abrasive particles are aspiratedfrom a supply line by a jet of air under pressure, a chamber in whichsaid particles are mixed with the air to form an air-borne abrasivestream, and a blast nozzle having an orifice from which the abrasivestream is discharged, and wherein the abrasive material tends to clog upand form obstructions in said passageway during operation of theapparatus; the combination with said apparatus of means for clearingsaid nozzles when clogged comprising a movable member supported on thenozzle of each of said abrasive guns for closing the discharge orificeof said nozzle, spring means normally maintaining each of said membersin a position wherein the discharge orifice of the associated nozzle isopen, and means operatively connected to each of said members andoperable from a position remote from said guns for selectively movingsaid member against the force of said spring means into a positionwherein it closes the discharge orifice of the associated nozzle andthereby causes the air to flow back into the abrasive supply linethrough said passageway and clear whatever obstruction may existtherein.

4. In an abrasive blasting apparatus of the type embodying a pluralityof abrasive guns mounted in a normally closed cabinet for directingair-borne streams of abrasive material against exposed surfaces ofarticles within the cabinet which are to be abraded, each of said gunsincluding a passageway through which abrasive particles are aspiratedfrom a supply line by a jet of air under pressure, a chamber in whichsaid particles are mixed with the air to form an air-borne abrasivestream, and a blast nozzle having an orifice from which the abrasivestream is discharged, and wherein the abrasive material tends to clog upand form obstructions in said passageway during operation of theapparatus; the combination with said apparatus of means for clearingsaid nozzles when clogged comprising a member'movably mounted on each ofsaid abrasive guns for closing the discharge orifice of the nozzlethereof, means for normally retaining each of said members in a positionwherein the discharge orifice of the associated nozzle is open, andmanually actuatable means individual to each of said members for movingsaid member into a position wherein it closes the discharge orifice ofthe associated nozzle and thereby causes the air to flow back into theabrasive supply line through said passageway and clear whateverobstruction may exist therein.

5. Apparatus for sand blasting bricks comprising a b casing throughwhich bricks are adapted to be moved, a plurality of sand biasing gunsmounted in said casing for directing air-borne streams of sand againstexposed surfaces of said bricks, each of said guns including a bodyhaving connections to a source of air under pressure and a supply ofsand, a passageway within said body through which sand is aspirated bythe air, a chamber in which the sand and air are mixed, and a nozzlethrough which the mixture of sand and air is discharged as a highvelocity abrading stream, and means for clearing said guns ofobstructions to the discharge of such abrading streams from said nozzlesincluding a movable member carried by each of said gun bodies having aplug for closing the discharge end of the associated nozzle, means fornormally maintaining each of said members and the associated plug in aposition out of the path of the abrading stream issuing from theassociated nozzle, and means operable from a position outside saidcasing for moving each of said members individually into a positionwhere-in the plug thereof closes the discharge end of the associatednozzle and causes the air to flow backwardly through said chamber andpassageway toward the sand supply, thereby clearing the gun of whateverobstruction may exist therein.

6. Apparatus for sand blasting bricks comprising a casing through whichbricks are adapted to be moved, a plurality of sand blasting gunsmounted in said casing for directing air-borne streams of sand againstexposed surfaces of said bricks, a sand hopper, a plurality of sandconduits each having one end connected to one of said guns for supplyingsand thereto and the other end removably inserted in said sand hopper,each of said guns including a body having a connection to a source ofair under pressure and another connection to one of said sand conduits,a passageway Within said body through which sand is aspirated by theair, a chamber in which the sand and air are mixed, and a nozzle havingan orifice through which the mixture of sand and air is discharged as ahigh velocity abrading stream, and means for clearing said guns ofobstructions to the discharge of such abrading streams from said nozzlesincluding a movable member supported on the nozzle of each of said gunbodies for closing the discharge orifice of said nozzle, yieldable meansfor normally maintaining each of said members in a position wherein thedischarge orifice of the associated nozzl is open, and means operablefrom a position adjacent said sand hopper for moving each of saidmembers individually into a position wherein it closes the dischargeorifice of the associated nozzle and causes the air to flow backwardlythrough said chamber, passageway and sand conduit, thereby clearing thegun of Whatever obstruction may exist therein.

7. Sand blasting apparatus as claimed in claim 6 wherein said last-namedmeans comprises a cable connected at one end to each of said members,extending therefrom to a position outside said casing and havingconnected to its other end means for applying a pull to.

said cable to move said member into the position wherein it closes thedischarge orifice of the associated nozzle.

8. Sand blasting apparatus as claimed in. claim 7 wherein the means forapplying a pull to each cable is a manually actuatable toggle locatedadjacent the sand hopper.

9. Sand blasting apparatus as claimed in claim 7 wherein the means forapplying a pull to each cable comprises a solenoid to which the cable isconnected and a manually actuatable switch for energizing said solenoidlocated adjacent the sand hopper.

l0. Mechanism for clearing obstructions from an abrasive blasting gun ofthe type including a body adapted to be connected to a source of airunder pressure and to a supply of abrasive material having therewithin apassageway through which the abrasive material may be aspirated by theair and a chamber in which the air and abrasive material maybe mixed,and a blast nozzle carried by said body having a discharge orificethrough which the mixture of air and abrasive material may be dischargedas an air-borne abrasive stream, said mechanism comprising a movablemember for closing the discharge orifice of said nozzle, means fornormally maintaining said member in a position adjacent said body butoutside the path of the abrasive stream issuing from said orifice, andmeans operable from a position remote from said gun body for moving saidmember from its normal position into a position wherein it closes saidorifice.

11. Mechanism for clearing obstructions from an abrasive blasting gun ofthe type including a body adapted to be connected to a source of airunder pressure and to a supply of abrasive material having therewith apassageway through which the abrasive material may be aspirated by theair and a chamber in which the air and abrasive material may be mixed,and a blast nozzle carried by said body having a discharge orificethrough which the mixture of air and abrasive material may be dischargedas an air-borne abrasive stream, said mechanism comprising a supportingbracket adapted to be mounted on said nozzle, a member pivotallysupported by said bracket having a portion thereof which is movable intoand out of a position wherein it closes the discharge orifice of saidnozzle, yieldable means for normally maintaining said member in aposition wherein the discharge orifice of said nozzle is open, and meansoperable from a position remote from said gun body for moving saidmember from its normal position into the position wherein said orificeis closed.

12. Mechanism for clearing obstructions from an abrasive blasting gun ofthe type including a body adapted to be connected to a source of airunder pressure and to a supply of abrasive material having therewithin apassageway through which the abrasive material may be aspirated by theair and a chamber in which the air and abrasive material may be mixed,and a blast nozzle carried by said body having a discharge orificethrough which the mixture of air and abrasive material may be dischargedas an air-borne abrasive stream, said mechanism comprising a supportingbracket adapted to be mounted on said nozzle and to extend at rightangles to the axis thereof, a lever member pivotally supported by saidbracket and carrying at one end thereof a plug for closing the dischargeorifice of said nozzle, spring means connecting said bracket and saidlever member and so arranged as to normally maintain said member in aposition wherein the discharge orifice of the nozzle is open, and meansconnected to said lever member and operable from a position remote fromsaid gun body for moving said member against the force of said springmeans into a position wherein said plug closes said discharge orifice.

l3. Mechanism for clearing obstructions from an abrasive blasting gun ofthe type including a body adapted to be connected to a source of airunder pressure and to a supply of abrasive material having therewithin apassageway through which the abrasive material may be aspirated by theair and a chamber in which the air and abrasive material may be mixed,and a blast nozzle carried by said body having a discharge orificethrough which the mixture of air and abrasive material may be dischargedas an air-borne abrasive stream, said mechanism comprising a supportingbracket adapted to be mounted on said nozzle and to extend at rightangles to the axis thereof, a substantially L-shaped lever memberpivotally supported adjacent the end of one of its arms by said bracketand carrying adjacent the end'of its other arm a plug ofabrasive-resistant material for closing the discharge orifice of saidnozzle, a tension spring so connecting said bracket and said levermember as to normally maintain said member in a position wherein theplug-carrying arm lies substantially parallel to the axis of said nozzleand outside the path of the abrasive stream issuing from said dischargeorifice, and means connected to said lever member at a pointintermediate its pivot point and said plug and operable from a positionremote from said gun body for spamee I 10 moving said member against theforce of said spring into 15?. Mechanism as claimed in claim 14,including a position wherein the plug-carrying arm is substantiallymeans carried by said bracket for guiding said cable. perpendicular tothe nozzle axis and said plug closes 331d dlscharge Onfice- ReferencesCited in the file of this patent 14-, Mechanism as claimed in claim 13wherein said mm last-named means comprises a flexible cable connected at5 UNITED STAUZS PATENTS one end to said lever member and havingconnected to its 1,829,661 Krautzberger Oct. 27, 1931 other end manuallyactuatable means for applying a pull 2,283,762 Robinson May 19, 1942 tosaid cable. 2 ,676,844 Paasche Apr. 27, 1954

